This invention relates to a system and method for non-invasive electrocardiographic imaging (xe2x80x9cECGIxe2x80x9d). More particularly, the invention is directed to a system and method using recorded body surface potentials that are noninvasively obtained and combined with data representing the geometry of a body torso to generate electrocardiographic images representing electrical activity of the heart.
While the invention is particularly directed to the art of noninvasive electrocardiographic imaging, and will thus be described with specific reference thereto, it will be appreciated that the invention may have usefulness in other fields and applications.
Cardiac electrical activity is a complex process that is both time dependent and spatially distributed throughout the myocardium. However, standard electrocardiographic techniques (i.e., ECG and vectorcardiography, VCG) are very limited in their ability to provide information on regional electrocardiac activity and to localize bioelectric events in the heart (in fact, VCG lumps all cardiac sources into a single dipole).
With recent advances in electronics and computers, simultaneous potential recordings from many (100 to 250) torso sites has become practical and inexpensive. The resulting body surface potential maps (BSPMs) over the entire torso surface have been shown to reflect regional electrical activity in the heart in a fashion that is not possible from conventional ECG techniques. However, BSPM techniques only provide a very low resolution, smoothed-out projection of cardiac electrical activity. Therefore, specific location of cardiac events (e.g., sites of initiation of activation or ectopic foci) and details of regional activity (e.g., number and location of activation fronts in the heart) cannot be determined merely from visual inspection of the BSPM.
In contrast, potential distributions over the epicardial surface of the heart accurately mirror details of the electrical events within the myocardium with high resolution. As a result, mapping of potentials directly from the epicardium has become an important experimental tool in the study of cardiac excitation and arrhythomogenesis. It has also become an essential clinical tool for diagnosis of arrhythmias, evaluation of treatment (e.g. antiarrhythmic drug therapy) and localization of cardiac electrical events (e.g. determining the location of the arrhythomogenic focus prior to ablation).
With the increasingly widespread use of nonpharmacological antiarrhythmic interventions (e.g. ablation), there is a growing need for fast and precise localization of electrocardiac events. It is highly desirable, therefore, to develop an imaging modality for the noninvasive reconstruction of epicardial potentials from BSPM data. Such an imaging modality could also be used, noninvasively, to identify patients at risk of arrhythmias and sudden death, and to evaluate the effects of intervention (e.g., drug therapy) in such patients.
The present invention provides a new and improved system and method for electrocardiographic imaging that overcomes the problems and difficulties of prior known systems.
An object of the present invention is to provide a system and method for noninvasively determining electrical activity on the surface of the heart of a human being wherein electrical potentials on the surface of the torso are monitored and body surface potential data, or maps, are then generated based on the electrical potentials determined. The geometry of the torso, locations of electrodes, the epicardial surface (or envelope) and position of the heart within the torso are then determined. A matrix of transformation is generated based on that data and regularized. An electrical potential distribution over the surface of the heart is then determined based on the regularized matrix of transformation and the body surface potential map. Electrograms and isochrones are also reconstructed on the epicardium.
In another aspect of the invention, the electrodes are disposed on a vest that is worn by the patient.
In another aspect of the invention, the geometry of the torso, the location of the electrodes, the epicardial surface (or envelope) and the position of the heart are determined by conducting a computed tomographic (CT) or magnetic resonance imaging (MRI) scan.
In another aspect of the invention, the geometry of the torso, the epicardial surface (or envelope) and the position of the heart are determined by conducting a biplane x-ray procedure.
In another aspect of the invention, determining the location of the electrodes and torso geometry includes implementing a digitizer.
In another aspect of the invention, determining the electrical potential distribution over the surface of the heart includes multiplying the regularized matrix of transformation by the body surface potential map.
In another aspect of the invention, epicardial electrograms are computed based on the electrical potential distribution.
In another aspect of the invention, isochrones are generated based on a derivative of the electrograms.
In another aspect of the invention, a system for implementing the above procedure is provided.
Further scope of the applicability of the present invention will become apparent from the detailed description provided below. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art.